Musical Plan (ミュージカルプラン Myūjikaru Puran) was a Japanese music company that specialized in composing music for media including video games. The company was founded by Noriyuki Nakagami, who oversaw the development of audio. The company was hired by Data East (and once by Pack-In-Video). While the company wasn't really a game developer, they did develop a few music programs for the Famicom; Ikinari Musician, Family Composer.
Most of their video games did not have credits. This was probably due to the publishers not allowing credits or the decision of the programmers.
NES / Famicom Disk System
The sound driver was programmed by Yasuo Miyata. Then the music was composed and arranged by K. Suzuki (and sometimes other composers). The music was written in Music Macro Language in the source code of Miyata's driver, then the music was played back being compiled into an emulator. It was an arduous process.